Begin work on MAC field processing

1 files changed, 95 insertions, 0 deletions

diff --git a/src/handshake/macs.rs b/src/handshake/macs.rs
new file mode 100644
index 0000000..c8b97e3
--- /dev/null
+++ b/src/handshake/macs.rs
@@ -0,0 +1,95 @@
+use std::time::Instant;
+
+use blake2::Blake2s;
+use subtle::ConstantTimeEq;
+use x25519_dalek::PublicKey;
+
+use zerocopy::{AsBytes, ByteSlice, FromBytes, LayoutVerified};
+
+const LABEL_MAC1: &[u8] = b"mac1----";
+const LABEL_COOKIE: &[u8] = b"cookie--";
+
+const SIZE_COOKIE: usize = 16;
+const SIZE_MAC: usize = 16; // blake2s-mac128
+
+macro_rules! HASH {
+    ( $($input:expr),* ) => {{
+        use blake2::Digest;
+        let mut hsh = Blake2s::new();
+        $(
+            hsh.input($input);
+        )*
+        hsh.result()
+    }};
+}
+
+macro_rules! MAC {
+    ( $key:expr, $($input:expr),* ) => {{
+        use blake2::VarBlake2s;
+        use digest::Input;
+        use digest::VariableOutput;
+        let mut tag = [0u8; SIZE_MAC];
+        let mut mac = VarBlake2s::new_keyed($key, SIZE_MAC);
+        $(
+            mac.input($input);
+        )*
+        mac.variable_result(|buf| tag.copy_from_slice(buf));
+        tag
+    }};
+}
+
+#[repr(C)]
+#[derive(Copy, Clone, FromBytes, AsBytes)]
+pub struct MacsFooter {
+    pub f_mac1: [u8; SIZE_MAC],
+    pub f_mac2: [u8; SIZE_MAC],
+}
+
+impl Default for MacsFooter {
+    fn default() -> Self {
+        Self {
+            f_mac1: [0u8; SIZE_MAC],
+            f_mac2: [0u8; SIZE_MAC],
+        }
+    }
+}
+
+struct Generator {
+    mac1_key: [u8; 32],
+    cookie_value: [u8; 16],
+    cookie_birth: Option<Instant>, // when was the cookie set?
+}
+
+impl Generator {
+    fn new(pk: PublicKey) -> Generator {
+        Generator {
+            mac1_key: HASH!(LABEL_MAC1, pk.as_bytes()).into(),
+            cookie_value: [0u8; SIZE_COOKIE],
+            cookie_birth: None,
+        }
+    }
+
+    fn mac1(&self, msg: &[u8]) -> [u8; SIZE_MAC] {
+        MAC!(&self.mac1_key, msg)
+    }
+
+    fn mac2(&self, msg: &[u8]) -> [u8; SIZE_MAC] {
+        MAC!(&self.cookie_value, msg)
+    }
+
+    pub fn set_cookie(&mut self, cookie: &[u8; SIZE_COOKIE]) {
+        self.cookie_birth = Some(Instant::now());
+        self.cookie_value = *cookie;
+    }
+
+    pub fn generate(&self, msg: &[u8]) -> MacsFooter {
+        MacsFooter {
+            f_mac1: self.mac1(msg),
+            f_mac2: self.mac2(msg),
+        }
+    }
+}
+
+struct Validator {}
+
+impl Validator {}